1. Field of the Invention
The present invention relates generally to methods for fabricating magnetic sensor elements. More particularly, the present invention relates to methods for fabricating dual stripe magnetoresistive (DSM) sensor elements with enhanced signal amplitudes.
2. Description of the Related Art
The recent and continuing advances in computer and information technology have been made possible not only by the correlating advances in the functionality, reliability and speed of semiconductor integrated circuits, but also by the correlating advances in the storage density and reliability of direct access storage devices (DASDs) employed in digitally encoded magnetic data storage and retrieval.
Storage density of direct access storage devices (DASDs) is typically determined as areal storage density of a magnetic data storage medium formed upon a rotating magnetic data storage disk within a direct access storage device (DASD) magnetic data storage enclosure. The areal storage density of the magnetic data storage medium is determined largely by the track width, the track spacing and the linear magnetic domain density within the magnetic data storage medium. The track width, the track spacing and the linear magnetic domain density within the magnetic data storage medium are in turn determined by several principal factors, including but not limited to: (1) the magnetic read-write characteristics of a magnetic read-write head employed in reading and writing digitally encoded magnetic data from and into the magnetic data storage medium; (2) the magnetic domain characteristics of the magnetic data storage medium; and (3) the separation distance of the magnetic read-write head from the magnetic data storage medium.
With regard to the magnetic read-write characteristics of magnetic read-write heads employed in reading and writing digitally encoded magnetic data from and into a magnetic data storage medium, it is known in the art of magnetic read-write head fabrication that magnetoresistive (MR) sensor elements employed within magnetoresistive (MR) read-write heads are generally superior to other types of magnetic sensor elements when employed in retrieving digitally encoded magnetic data from a magnetic data storage medium. In that regard, magnetoresistive (MR) sensor elements are generally regarded as superior since magnetoresistive (MR) sensor elements are known in the art to provide high output digital read signal amplitudes, with good linear resolution, independent of the relative velocity of a magnetic data storage medium with respect to a magnetoresistive (MR) read-write head having the magnetoresistive (MR) sensor element incorporated therein. Within the general category of magnetoresistive (MR) sensor elements, dual stripe magnetoresistive (DSMR) sensor elements, and in particular longitudinal patterned exchange biased dual stripe magnetoresistive (DSMR) sensor elements, are presently of considerable interest insofar as the multiple magnetically biased magnetoresistive (MR) layers employed within longitudinally patterned exchange biased dual stripe magnetoresistive (DSMR) sensor elements typically provide enhanced magnetic read signal amplitude and fidelity in comparison with, for example, soft adjacent layer (SAL) magnetoresistive (MR) sensor elements.
While longitudinal patterned exchange biased dual stripe magnetoresistive (DSMR) sensor elements are thus desirable within the art of digitally encoded magnetic data storage and retrieval, longitudinal patterned exchange biased dual stripe magnetoresistive (DSMR) sensor elements are nonetheless not entirely without problems within the art of digitally encoded magnetic data storage and retrieval. In particular, as a data track width within a magnetic medium employed within digitally encoded magnetic data storage and retrieval decreases, it becomes increasingly important that a read track width within a longitudinal patterned exchange biased dual stripe magnetoresistive (DSMR) sensor element employed in reading the data within the data track be uniformly magnetically biased. Uniform magnetic bias profiles are desirable within read track widths of longitudinal patterned exchange biased dual stripe magnetoresistive (DSMR) sensor elements since such uniform magnetic bias profiles provide for optimal magnetic read signal amplitudes within such longitudinal patterned exchange biased dual stripe magnetoresistive (DSMR) sensor elements.
It is thus towards the goal of providing, for use within magnetic data storage and retrieval, a longitudinal patterned exchange biased dual stripe magnetoresistive (DSMR) sensor element with a uniform magnetic bias profile across a read track width of the longitudinal patterned exchange biased dual stripe magnetoresistive (DSMR) sensor element that the present invention is most generally directed.
Various methods and resultant magnetic sensor element structures have been disclosed in the art of magnetic sensor element fabrication for forming magnetically biased magnetic sensor elements with enhanced functionality, enhanced reliability or other desirable properties.
For example, general considerations pertinent to both intrinsic and extrinsic longitudinal magnetic biasing of magnetoresistive (MR) layers within magnetoresistive (MR) sensor elements, including but not limited to dual stripe magnetoresistive (DSMR) sensor elements, are disclosed within Ashar, Magnetic Disk Drive Technology: Heads, Media, Channel, Interfaces and Integration, IEEE, Inc., New York, 1997, pp. 142-46.
In addition, several disclosures specifically directed towards improved magnetic biasing within single stripe magnetoresistive (SSMR) sensor elements may also be found within the art of magnetoresistive (MR) sensor element fabrication. Included within such disclosures are: (1) Kuriyama, in U.S. Pat. No. 5,592,082 (a single stripe magnetoresistive (SSMR) sensor element employing a magnetoresistive (MR) layer having formed thereupon a series of patterned permanent magnet biasing layers which are formed at an angle of about 45 degrees with respect to a major axis of the magnetoresistive (MR) layer to attenuate noise within the magnetoresistive (MR) layer); and (2) Kung et al., in U.S. Pat. No. 5,680,281 (a single stripe magnetoresistive (MR) sensor element which may be magnetically biased employing only a uniaxial anisotropy of a magnetoresistive (MR) layer and a shape anisotropy of an active region of the magnetoresistive (MR) layer).
Further, several disclosures specifically directed towards improved magnetic biasing within soft adjacent layer (SAL) magnetoresistive (MR) sensor elements may also be found within the art of magnetic sensor element fabrication. Included within such disclosures are: (1) Chen et al., in U.S. Pat. No. 5,285,339 (a soft adjacent layer (SAL) magnetoresistive (MR) sensor element formed employing a magnetoresistive (MR) layer formed from a magnetic material having a low uniaxial magnetic anisotropy separated from a magnetic biasing soft adjacent layer (SAL) formed from a magnetic material having a high uniaxial magnetic anisotropy); (2) Chen et al., in U.S. Pat. No. 5,325,253 (a soft adjacent layer (SAL) magnetoresistive (MR) sensor element employing a pair of patterned antiferromagnetic magnetic biasing layers formed upon a pair of opposite ends of a magnetoresistive (MR) layer, where the pair of patterned antiferromagnetic magnetic biasing layers has a canted exchange bias field with respect to the magnetoresistive (MR) layer); and (3) Gill et al., in U.S. Pat. No. 5,508,866 (a soft adjacent layer (SAL) magnetoresistive (MR) sensor element where the soft adjacent layer (SAL) is further magnetically biased and stabilized by an antiferromagnetic magnetic bias layer of nickel oxide).
Finally, several disclosures which are directed more specifically towards dual stripe magnetoresistive (DSMR) sensor elements, and may include longitudinal magnetic biasing considerations of such dual stripe magnetoresistive (DSMR) sensor elements, may also be found within the art of magnetoresistive (MR) sensor element fabrication. Included within such disclosures are: (1) Smith, in U.S. Pat. No. 5,406,433 (a dual stripe magnetoresistive (DSM) sensor element where each magnetoresistive (MR) layer is fabricated with a height at least ten times a trackwidth of the dual stripe magnetoresistive (DSMR) sensor element, such that the dual stripe magnetoresistive (DSMR) sensor element may be employed for sensing magnetic signals of increased linear density and decreased track spacing); and (2) Shi et al., in U.S. Pat. No. 5,684,658 (a dual stripe magnetoresistive (DSMR) sensor element where a first trackwidth of a first magnetoresistve (MR) layer is physically offset from a second trackwidth of a second magnetoresistive (MR) layer, to provide in conjunction with an electromagnetic bias direction of the two magnetoresistive (MR) layers variable off-track performance characteristics of the dual stripe magnetoresistive (DSMR) sensor element).
Desirable within the art of longitudinal patterned exchange biased dual stripe magnetoresistive (DSMR) sensor element fabrication are additional methods and materials which may be employed for forming longitudinal patterned exchange biased dual stripe magnetoresistive (DSMR) sensor elements with enhanced magnetic bias uniformity of the longitudinal patterned exchange biased dual stripe magnetoresistive (DSMR) sensor elements within the trackwidths of the longitudinal patterned exchange biased dual stripe magnetoresistive (DSMR) sensor elements.
It is towards the foregoing object that the present invention is directed.
A first object of the present invention is to provide a longitudinal patterned exchange biased dual stripe magnetoresistive (DSMR) sensor element, and a method for fabricating the longitudinal patterned exchange biased dual stripe magnetoresistive (DSMR) sensor element, where the longitudinal patterned exchange biased dual stripe magnetoresistive (DSMR) sensor element has an enhanced magnetic bias profile uniformity within a trackwidth of the longitudinal patterned exchange biased dual stripe magnetoresistive (DSMR) sensor element.
A second object of the present invention is to provide a longitudinal patterned exchange biased dual stripe magnetoresistive (DSMR) sensor element and a method for fabricating the longitudinal patterned exchange biased dual stripe magnetoresistive (DSMR) sensor element in accord with the first object of the present invention, which method is readily commercially implemented.
In accord with the objects of the present invention, there is provided by the present invention a longitudinal patterned exchange biased dual stripe magnetoresistive (DSMR) sensor element and a method for fabricating the longitudinal patterned exchange biased dual stripe magnetoresistive (DSMR) sensor element. To practice the method of the present invention, there is first provided a substrate. There is then formed over the substrate a patterned first magnetoresistive layer. There is then formed contacting a pair of opposite ends of the patterned first magnetoresistive (MR) layer a pair of patterned first magnetic biasing layers, where the pair of patterned first magnetic biasing layers is biased in a first transverse magnetic bias direction substantially perpendicular with a first axis of the patterned first magnetoresistive (MR) layer which separates the pair of patterned first magnetic biasing layers. There is then formed separated from the patterned first magnetoresistive (MR) layer by a non-magnetic spacer layer a patterned second magnetoresistive (MR) layer. There is then formed contacting a pair of opposite ends of the patterned second magnetoresistive (MR) layer a pair of patterned second magnetic biasing layers separated by a second axis of the patterned second magnetoresistive (MR) layer which is substantially parallel with the first axis of the patterned first magnetoresistive (MR) layer, where the pair of patterned second magnetic biasing layers is biased in a second transverse magnetic bias direction substantially anti-parallel with the first transverse magnetic bias direction. Within the method of the present invention, the pair of patterned first magnetic biasing layers and the pair of patterned second magnetic biasing layers are formed of a single magnetic biasing material. Similarly, within the method of the present invention, the pair of patterned second magnetic biasing layers is biased employing a first thermal annealing method employing a first thermal annealing temperature, a first thermal annealing exposure time and a first extrinsic magnetic bias field strength such that the pair of patterned second magnetic biasing layers is biased in the second transverse magnetic bias direction while the pair of patterned first magnetic biasing layers is not substantially demagnetized from the first transverse magnetic bias direction while forming a pair of partially demagnetized patterned first magnetic biasing layers from the pair of patterned first magnetic biasing layers. Finally, there is then annealed thermally the substrate while employing a second thermal annealing method employing a second thermal annealing temperature, a second thermal annealing exposure time and a second extrinsic magnetic bias field substantially parallel with the first axis and the second axis such that the first transverse magnetic bias direction of the pair of partially demagnetized patterned first magnetic biasing layers is canted in the direction of the second extrinsic magnetic bias field to form a pair of canted partially demagnetized patterned first magnetic biasing layers and the second transverse bias direction of the patterned second magnetic biasing layers is canted in the direction of the second extrinsic magnetic bias field to form a pair of canted patterned second magnetic biasing layers.
The method of the present invention contemplates a magnetically biased dual stripe magnetoresistive (DSMR) sensor element fabricated in accord with the method of the present invention.
The present invention provides a magnetically biased dual stripe magnetoresistive (DSMR) sensor element, and a method for fabricating the magnetically biased dual stripe magnetoresistive (DSMR) sensor element, where the magnetically biased dual stripe magnetoresistive (DSMR) sensor element has an enhanced magnetic bias profile uniformity within a read trackwidth of the magnetically biased dual stripe magnetoresistive (DSMR) sensor element. The present invention realizes the foregoing object by employing when forming the magnetically biased dual stripe magnetoresistive (DSMR) sensor element a first magnetoresistive (MR) layer biased employing a pair of canted partially demagnetized patterned first magnetic biasing layers and a second magnetoresistive (MR) layer biased employing a pair of canted patterned second magnetic biasing layers, where the foregoing two pair of canted magnetic biasing layers are canted in opposite directions.
The method of the present invention is readily commercially implemented. The method of the present invention employs thermal annealing methods which are generally known in the art of magnetoresistive (MR) sensor element fabrication. Since it is a process control within the present invention which provides at least in part the method of the present invention, rather than the existence of methods and materials which provides the present invention, the method of the present invention is readily commercially implemented.
Advantageously, a magnetically biased dual stripe magnetoresistive (DSMR) sensor element formed in accord with the method of the present invention is formed with a pair of patterned first magnetic biasing layers and a pair of patterned second magnetic biasing layers formed of a single magnetic biasing material, since a pair of patterned second magnetic biasing layers is transversely magnetically biased in a second magnetic bias direction employing a thermal annealing method employing a thermal annealing temperature, a thermal annealing exposure time and an extrinsic magnetic bias field strength such that a pair of patterned first magnetic biasing layers is not appreciably demagnetized from a first magnetic bias direction anti-parallel the second magnetic bias direction.